For many companies, social media is something the marketing department uses to increase their reach. Features like Facebook Connect seem like obligatory add-ons. But part of the company’s core offering? Not so much.

That’s about to change. So says Silicon Valley mega-investor John Doerr, of Kleiner Perkins Caulfield & Byers, who today announced a $250 million fund to invest in social applications and services. Companies like Cafebots, a startup Kleiner Perkins invested in earlier this year that helps people manage their online social relationships.

Also investing in the new "sFund" are Amazon, Facebook, and Zynga, whose CEOs appeared with Doerr at an event on the Facebook campus. The three other backers are Comcast, Liberty Media, and Allen & Company. The fund kicks off today and has not made any investments yet.

Doerr said KPCB was motivated to create the fund because it believes there’s a "third wave" of "incredible and disruptive innovation" that is fundamentally changing the nature of the Web right now. The first was the creation of the Internet itself, and the second was the invention of browsers, which made it possible for everyday people to use the Web. Now, Doerr said, the Web is shifting "from an old Internet of documents and sites to a new one that’s all about people and places and relationships." The sFund’s goal, Doerr said, is not only to invest in companies that are leading the charge into the new era, but also to inspire young entrepreneurs to take the plunge.

Kleiner Perkins, one of Sand Hill Road’s leading venture capital firms, has a history of picking winners like Google, Amazon, and Sun Microsystems, as well as Electronic Arts, Symantec, and Netscape. In 2008, Kleiner Perkins created the $100 million iFund to invest in developers making applications, services, and components for the iPhone and iPad. One of those companies, game developer Ngmoco, just got bought by Japanese mobile gaming giant DeNA Co. for $400 million.

So when Kleiner Perkins—or, in this case, Mark Zuckerberg of sFund partner Facebook—says "every industry is going to get fundamentally rethought and designed around people," it might be worth taking a listen.

Bing Gordon, the former Electronic Arts creative director who is now a KPCB partner, will run the fund. Companies today, he said, need to have a social sensibility at their core. Those that see social as something to be slapped on afterwards will get left behind.

"In the videogame business, we called the ‘slap-on’ [stuff] ‘shovelware,’" Gordon said. "So an entrepreneur who walks in [to a meeting with the sFund] with a shovel will probably have a shorter meeting than someone who walks in with a ground-up new architecture."

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